Rheostatic safety braking for electrical motorization systems

Abstract

Safety braking device (10) for an electric motorized system, comprising: a polyphase motor (11) comprising a frame (12) forming a stator and a rotor (13) mounted in the frame (12) to pivot about an axis of rotation; at least one dissipative circuit (14) per phase of the motor comprising a plurality of braking resistors (15) and a plurality of activation switches (16) for the braking resistors; a plurality of connection switches (17) each connecting one of the dissipative circuits (14) to one of the phases of the motor and a control unit (30) connected to the switches to control them; the braking resistors (15) being arranged on the frame (12) and the activation switches (16) and the connection switches (17) being grouped together in an electrical box (18) fixed to the frame (12). Electric motorized system (1) comprising such a device (10). ABSTRACT FIGURE: Fig. 2

Description

Title of the invention: Rheostatic safety braking for electrical motorization systems

[0001] The present invention relates to the field of electric motors and more particularly to safe braking for electrical motorization systems. BACKGROUND OF THE INVENTION

[0002] In the field of safe braking of electric motorized systems, different conventional solutions exist such as regenerative braking (in an accumulator such as a battery or a supercapacitor) or dissipative braking (generally by heat dissipation in a resistor). These safe braking modes are implemented when braking in normal mode is no longer ensured. For example, the safe braking mode is implemented when loss due to failure or disconnection of electrical and / or electronic equipment.

[0003] An electrical motorization system comprises, according to a conventional architecture, an electric motor, an inverter connected to the phases of the motor via control switches, a battery connected via a charge / discharge switch to a connection line to the inverter, a dissipating resistor (or clamp resistor) connected by a connection / disconnection switch to the connection line to the inverter, a control unit for controlling the inverter and the various switches according to signals supplied by sensors and control instruments. Safe braking is ensured either by opening the charge / discharge switch and controlling the inverter so as to short-circuit the phases of the motor or by closing the connection / disconnection switch to dissipate the current in the dissipating resistor.

[0004] The braking resistor is generally sized to provide braking at the maximum speed of the system speed range.

[0005] Conventional architecture therefore does not allow optimal braking over the entire speed range of the system. In addition, the elements arranged in the immediate environment of this resistance must be sized to be able to withstand or dissipate the heat produced by the dissipating resistance.

[0006] This results in additional financial costs, an increase in mass and impacts on the reliability of the equipment.

[0007] Climate change is a major concern for many legislative and regulatory bodies around the world. Indeed, various restrictions on carbon emissions have been, are being or will be adopted by various states. In particular, an ambitious standard applies both to new types of aircraft but also those in circulation requiring the implementation of technological solutions in order to make them compliant with current regulations. Civil aviation has been mobilizing for several years now to contribute to the fight against climate change.

[0008] Technological research efforts have already made it possible to significantly improve the environmental performance of aircraft. The Applicant takes into consideration the impact factors in all phases of design and development to obtain less energy-intensive, more environmentally friendly aeronautical components and products whose integration and use in civil aviation have moderate environmental consequences with the aim of improving the energy efficiency of aircraft.

[0009] To this end, the invention is the result of technological research aimed at very significantly improving the performance of aircraft and, in this sense, contributes to reducing the environmental impact of aircraft.

[0010] Furthermore, in the event of failure of the connection / disconnection switch and the inverter, there is no longer any safe braking solution. SUBJECT OF THE INVENTION

[0011] The invention particularly aims at providing a safe braking method for electrical motorization systems, at least partially overcoming the aforementioned drawbacks. Summary of the invention

[0012] To this end, according to the invention, there is provided a safety braking device for an electrical motorization system, comprising: - a polyphase motor comprising a frame forming a stator and a rotor mounted in the frame to pivot around an axis of rotation; - at least one dissipative circuit per phase of the motor comprising a plurality of braking resistors and a plurality of braking resistor activation switches; - a plurality of connection switches each connecting one of the dissipative circuits to one of the phases of the motor; and - a control unit connected to the switches to control them.

[0013] The braking resistors are arranged on the casing and the activation switches and the connection switches are grouped in an electrical box fixed to the casing.

[0014] Thus, the present invention advantageously proposes a new safe braking solution allowing, by adjusting the number of resistors connected to each phase of the motor, to effectively brake an electric motor over its entire speed range. Furthermore, this solution makes it possible to minimize costs, to limit the

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[0023] overall mass of the electrical motorization system in which the safety braking device is integrated and to improve the reliability of the electrical system. In addition, the arrangement of the braking resistors on the motor limits the constraints linked to heating of the resistors since the mass of the motor casing is used to dissipate the heat and makes it possible to limit the size of the electric motorization system. Depending on optional features, used individually or in whole or in part in combination: - the braking resistors of each dissipative circuit are arranged in parallel with each other; - each of the dissipative circuits is provided with three braking resistors; - each of the dissipative circuits is provided with three activation switches braking resistors; - the activation switches and the connection switches are carried by at least one electronic card arranged in the electrical box; - at least one inductance is arranged in the dissipative circuit; - at least one of the braking resistors comprises a section extending parallel to the rotor rotation axis; - at least one of the braking resistors comprises a section extending in an arc around the axis of rotation of the rotor. The invention also relates to an electric motorized system comprising a drive motor and a safety braking device as mentioned above, the safety braking device itself being connected to an inverter via a plurality of switches, the inverter being connected to an accumulation device. The invention also relates to an electrical motorization system incorporating such a device. Other characteristics and advantages of the invention will emerge from reading the following description of a particular and non-limiting embodiment of the invention. Brief description of the drawings Reference will be made to the attached drawings, including: [Fig.l] [Fig.l] is a functional diagram of an electrical motorization system comprising a safety braking device according to the invention; [Fig.2] [Fig.2] is a diagram partially representing the architecture of this electrical motorization system; [Fig.3] [Fig.3] is a schematic perspective view of the electrical motorization system; [Fig.4a] [Fig.4a] is a schematic end view of the engine according to a method of rea- lization of the invention;

[0024] [Fig.4b] [Fig.4b] is a schematic side view of the engine according to this method of rea lization of the invention;

[0025] [Fig.5] [Fig.5] is a schematic view of a switch included in the safety braking device for electric motorized systems illustrated in [Fig.3], according to one embodiment of the invention. DETAILED DESCRIPTION OF THE INVENTION

[0026] With reference to Figures 1 to 5, an electrical motorization system 1 is described comprising a safety braking device 10 associated with a polyphase, preferably three-phase, motor 11. The motor 11 comprises a casing 12 provided with electromagnetic windings (the phases) to form a stator, and a rotor 13 mounted in the casing 12 to pivot about an axis of rotation. The casing 12 is shaped as a tube and is arranged to protect the rotor 13 from the external environment and ensure the transfer of heat produced inside the motor to the outside of the motor 11. In a manner known per se, the casing 12 is made of aluminum or steel. The rotor 13 carries a plurality of permanent magnets and is mechanically connected to a source of kinetic energy 70 driving the rotation of the rotor. In a motor operating mode, the electromagnetic windings of the frame 12 are energized to generate a rotating stator electromagnetic field.In a “generator” operating mode, the electromagnetic windings of the frame 12 ensure the capture of a rotating rotor electromagnetic field. The safety braking device 10 also comprises a plurality of sensors internal to the motor 11.

[0027] With reference to [Fig.l], the electrical motorization system 1 comprises a set 90 of control switches each connecting one of the phases of the motor to an alternating current input / output circuit of an inverter 80 having a direct current input / output circuit connected, via a connection line, to a charge / discharge switch 60 connected to an energy storage member such as a battery 40.

[0028] The motorized electrical system 1 may also optionally comprise a dissipating member 50 comprising a dissipating resistor (or clamp resistor) 52 connected by a connection / disconnection switch 51 to the connection line to the inverter 80.

[0029] The safety braking device 40 is arranged on the motor 11.

[0030] The safety braking device 10 comprises a dissipative circuit 14 per phase of the motor 11. Preferably, the safety braking device 10 comprises three dissipative circuits 14, i.e. one dissipative circuit 14 for each of the phases of the motor 11. Each dissipative circuit 14 comprises a plurality of braking resistors 15 and a plurality of activation switches 16 for the braking resistors 15. Preferably, each dissipative circuit 14 comprises three braking resistors 15 (named: R11, R12, R13 for phase 1; R21, R22, R23 for phase 2; R31, R32, R33 for phase 3) and an activation switch 16 for each of the braking resistors 15, said activation switch 16 (named: TU for braking resistor RI 1, T12 for braking resistor R12, T13 for braking resistor R13, T21 for braking resistor R21, T22 for braking resistor R22, T23 for braking resistor R23, T31 for braking resistor R31, T32 for braking resistor R32, T33 for the re braking resistor R33) being connected in series to the braking resistor 15 which it activates. The braking resistors 15, responsible for transforming electrical energy into thermal energy, are arranged on the frame 12. Preferably, at least one of the braking resistors 15 comprises a section extending parallel to the axis of rotation of the rotor 13. Here, all the braking resistors 15 comprise a section extending parallel to the axis of rotation of the rotor 13.

[0031] In the embodiment described here, the braking resistor 15 / activation switch 16 pairs of each dissipative circuit 14 are arranged in parallel with each other.

[0032] Furthermore, the safety braking device 10 also comprises a plurality of connection switches 17 each arranged to connect one of the dissipative circuits 14 to one of the phases of the motor. The safety braking device 10 here comprises three connection switches 17, namely one for each phase of the motor.

[0033] Thus, the connection switch T4 allows, when it is closed, to connect the first dissipative circuit 14 to the first phase of the motor 11. The first dissipative circuit comprises, as mentioned previously, three activation switches 16, designated respectively by T1 1, T12 and T13. When the switch T1 1 is closed, it connects the phase 1 to the braking resistor RI 1 via the closed connection switch T4; when the switch T12 is closed, it connects the phase 1 to the braking resistor R12 via the closed connection switch T4; when the switch T13 is closed, it connects the phase 1 to the braking resistor R13 via the closed connection switch T4.

[0034] The connection switch T5 allows, when closed, to connect the second dissipative circuit 14 to the second phase of the motor. This second dissipative circuit comprises, as mentioned previously, three activation switches 16, designated respectively by T21, T22 and T23. When the switch T21 is closed, it connects phase 2 to the braking resistor R21 via the closed connection switch T5; when the switch T22 is closed, it connects phase 2 to the braking resistor R22 via connection switch T5 closed; when switch T23 is closed, it connects phase 2 to braking resistor R23 via connection switch T5 closed.

[0035] The connection switch T6 allows, when closed, to connect the third dissipative circuit 14 to the third phase of the motor. This third dissipative circuit comprises, as mentioned previously, three activation switches 16, designated respectively by T31, T32 and T33. When the switch T31 ​​is closed, it connects phase 3 to the braking resistor R31 via the closed connection switch T6; when the switch T32 is closed, it connects phase 3 to the braking resistor R32 via the closed connection switch T6; when the switch T33 is closed, it connects phase 3 to the braking resistor R33 via the closed connection switch T6.

[0036] For example, the activation switches 16 and the connection switches 17 each have a mass of between 50 and 70 grams. More precisely, the mass of each switch is estimated at 60 grams. Thus, since the braking device 10 comprises twelve switches 16, 17 (nine activation switches 16 and three connection switches 17), the overall mass of the switches 16, 17 is estimated at 720 grams.

[0037] The safety braking device 10 also comprises an electrical box 18. The electrical box 18 comprises at least one electronic card (not shown) carrying the activation switches 16 and the connection switches 17. The electrical box 18 is attached to the casing 12. In a manner known per se, the electrical box 18 is made of aluminum or steel. The electronic card(s) are fixed in the electrical box itself fixed to said casing 12 by a fixing system. The electrical box 18 is more precisely arranged at one end of the motor (the motor having two ends opposite each other along the axis of rotation of the rotor). A thermally conductive paste is arranged between the switches and the electronic card and / or between the electronic card and the electrical box 18.This thermally conductive paste allows thermal energy to be transferred from the switches to the electrical box 18. .

[0038] Finally, the safety braking device 10 comprises a plurality of connectors for powering and controlling the various electrical and electronic components of said safety braking device 10. For example, at least one electrical connector makes it possible to connect the electromagnetic windings to the switches 90.

[0039] The motorized electrical system 1 also comprises a control unit 30 connected to: - a plurality of sensors 20 arranged to detect operating states

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[0046] of the electrical motorization system; - to switches 51, 60, 90, 16, 17 to control them; - to battery 40 to be powered by it and monitor its operation; - to the inverter 80 to control it and monitor its operation; - at least one control instrument not shown to be controlled by it. In a normal generator operating mode of the electronic motorization system, the switches 51, 60 and 90 are controlled so that the generated energy is directly stored in the battery 40. Note that switches 51, 60, and 90 can be "normally open" or "normally closed." "Normally open" means that the circuit is energized when the switch is activated. Conversely, "normally closed" means that the circuit is energized by default and is open when the switch is activated. The system ensures safe braking by: - opening the charge / discharge switch 60 and controlling the inverter 80 so as to short-circuit the motor phases; - closing switches 16 and 17 to dissipate the current in the braking resistors 15; - closing the connection / disconnection switch 51 to dissipate the current in the dissipating resistor 52. We will now focus on the second braking mode, which is that of the invention, the other two being known. When one or more of the elements of the motorized electrical system 1 cease to function, the circuit switches to safe operating mode. From then on, the control unit 30 controls the switches 90 to open the motorized electrical system 1 and thus prevent the rotor 13 of the motor 11 from running out of speed. The control unit 30 also controls the safety braking device 10 to brake the rotor 13. It is recalled that, when the electromagnetic windings forming the phases of the motor 11 are not powered and the rotor 13, carrying the permanent magnets, rotates, an electromotive force is generated in the phases of the motor 11. When the phases of the motor 11 are short-circuited, the electromotive force generates short-circuit currents and therefore a braking torque. As a result, the braking torque depends on the electromotive force and the impedance of the motor 11 comprising at least one inductance and at least one resistance. The maximum braking torque is at a so-called “critical” speed. The objective is to control the braking torque over the entire range speed control through the control of impacting elements. Among these elements, the motor design is fixed. The inductance varies the maximum braking torque but does not impact the critical speed. On the other hand, the resistance varies the critical speed but does not impact the maximum braking torque. The resistance is independent of the current and is therefore easier to control.

[0047] Thanks to the invention, the resistance in question is the equivalent resistance of the resistors 15 connected to phases 1, 2 and 3 of the motor 11. The higher the equivalent resistance, the higher the critical speed. The maximum braking torque is therefore advantageously maintained over the entire speed range by controlling this equivalent resistance.

[0048] Thus, for a safe braking application, the speed is initially high and decreases as a function of time. The equivalent resistance is therefore controlled so that it is initially high and then decreases as a function of decreasing speed.

[0049] The speed of the engine is known by the control unit 30. Here, three speed ranges are delimited: the low speed range, the medium speed range and the high speed range.

[0050] The table below illustrates the different switch control configurations: Speed ​​Range Switch Status T4 / T5 / T6 T11 / T21 / T31 T12 / T22 / T32 T13 / T23 / T33 High Speed ​​Enabled Enabled Disabled Disabled Medium Speed ​​Enabled Enabled Disabled Low Speed ​​Enabled Enabled Enabled Enabled

[0051] Thus, regardless of the speed range considered, the connection switches 17 are all activated in safe braking mode. Furthermore, since the braking resistors 15 are arranged in parallel, the equivalent resistance obtained is high when few braking resistors 15 are connected to the motor phases. At high speed, the activation switches 16 activate only the first braking resistors 15 of the three dissipative circuits 14. At medium speed, the activation switches 16 activate the second braking resistors 15 of the three motor phases. The overall equivalent resistance therefore decreases since two resistors in parallel are now connected to each phase of the motor 11. In the same way, at low speed, the motor speed decreases and the activation switches 16 activate the third braking resistors 15 of the three motor phases. The re overall equivalent resistance decreases further since three resistors in parallel are now connected to each phase of motor 11.

[0052] Thus, with reference to [Fig.2], at high speed, the braking resistors RI 1, R21 and R31 are activated. At medium speed, the braking resistors R12, R22 and R32 are also activated. Therefore, since RI 1 is in parallel with R12, the equivalent resistance of the first phase of the motor decreases. In the same way, since R21 is in parallel with R22, the equivalent resistance of the second phase of the motor decreases. And in the same way, since R31 is in parallel with R32, the equivalent resistance of the third phase of the motor decreases. At low speed, the braking resistors R13, R23 and R33 are activated in addition to the other two of each dissipative circuit 14. Therefore, since RI 1 is in parallel with R12 and in parallel with R13, the equivalent resistance of the first phase of the motor decreases. Similarly, since R21 is in parallel with R22 and in parallel with R23, the equivalent resistance of the second phase of the motor decreases.Similarly, since R31 is in parallel with R32 and in parallel with R33, the equivalent resistance of the third phase of the motor decreases.

[0053] With reference to Figure 4, the aforementioned braking resistors 15 are precisely dimensioned. Thus, each braking resistor 15 is an enameled conductive wire wound in a zigzag pattern around the carcass 12 (of perimeter P and length L). Here, the braking resistors 15 comprise a section extending parallel to the length L. The zigzag winding makes it possible to cancel the induced voltage. To dimension the braking resistors 15, the following parameters of the winding must be determined: - the diameter of the wire, - the number of zigzags, - the number of layers, - the mass of the winding and - the size of the winding.

[0054] The enameled conductive wire is here enameled copper. The objective of the dimensioning is to obtain the right resistance and the right thermal mass in relation to the energy to be dissipated, through the choices of the diameter of the copper and the number of layers. The ideal thermal mass must be chosen so that the temperature of the winding does not exceed 200°C at the short-circuit current during the braking time.

[0055] The parameters to be taken into account, as input, for dimensioning are therefore the following: - the desired value of the braking resistor 15, - the overall braking time, - the braking time on a first resistance, and - the short-circuit current on this first resistance.

[0056] The overall braking time is estimated from the motor speed, the braking torque and the rotational inertia.

[0057] The braking time on a first resistor is estimated for each control step. The temperature is calculated here by the adiabatic method considered correct for 20 seconds. Beyond this period, the calculation is considered erroneous due to heat transfer. Depending on the needs, the resistor can be sized to meet the thermal requirements by the following method.

[0058] From the diameter of the bare conductive wire and the number of initial layers, the parameters are calculated as follows: - the diameter of the bare conductive wire Dcu is known, - the number of layers Nb layers is known, - the section of the bare conductive wire Scu is known, - the distance d is equal to the diameter of the enameled conductive wire = Dcu*coefficient, the coefficient being representative of the clearance between two enameled conductive wires (for example equal to 1.1), the number of zigzags Nb zigZagS = § *Nb layers, - the length of the bare conductive wire L f il = N b zigzags*L, the resistance _ resistivity, Scu - the total mass of the bare conductive wire Mat = density of bare conductive wire*Lfil*Scu, - the total mass of the enameled conductive wire Mbob = Mcu*coefficient = Lf it *Scu*siled enamelled conductor wire and - the thickness of the winding Ebob = d*Nb layers.

[0059] In [Fig. 5], a transistor circuit is shown that can be used to form the activation switches 16 and the connection switches 17. This transistor circuit comprises control pins 3, 4 and pins 1, 2 for connection to the elements between which the switch is placed (for example a phase of the motor 11 and the dissipative circuit 14). A direct current supplies the switch via pins 3 and 4. The direct current supply is activated or deactivated by the control unit 30. When the direct current supply is deactivated, a voltage of 0 volts is established between pins 3 and 4. This voltage does not allow the activation of the transistor shown in [Fig. 5]. This prevents the motor phase, connected to pin 1, from being connected to the braking resistors 15 of the dissipative circuit 14 connected to pin 2. When the DC supply is activated, strictly positive and sufficient to activate the transistor, then the connection between the motor phase and the braking resistors 15 of the dissipative circuit 14 is authorized.

[0060] Of course, the invention is not limited to the embodiment described but encompasses any variant falling within the scope of the invention as defined by the claims.

[0061] In particular, although here the braking resistors comprise a section extending parallel to the axis of rotation of the rotor, it is entirely conceivable that the braking resistors comprise a section extending in an arc of a circle around the axis of rotation of the rotor.

[0062] Although here the braking resistors are arranged on the casing, one parallel to the other, it is entirely conceivable that the braking resistors are arranged on the casing in series.

[0063] Although here the braking resistors are used alone, a safety braking system comprising braking resistors and inductors could be envisaged.

[0064] Although here the enameled electrically conductive wire is enameled copper, it is entirely conceivable that the enameled electrically conductive wire is made of another electrically conductive material such as aluminum.

[0065] The invention may comprise a different number of braking resistors and for example two or more than three braking resistors per dissipative circuit.

[0066] The electrical motorization system may be devoid of a dissipating member 50.

[0067] The battery 40 can be replaced by a supercapacitor.

Claims

Claims

1. Safety braking device (10) for an electric motorized system, comprising: - a polyphase motor (11) comprising a frame (12) forming a stator and a rotor (13) mounted in the frame (12) to pivot about an axis of rotation; - at least one dissipative circuit (14) per phase of the motor comprising a plurality of braking resistors (15) and a plurality of activation switches (16) for the braking resistors; - a plurality of connection switches (17) each connecting one of the dissipative circuits (14) to one of the phases of the motor and - a control unit (30) connected to the switches to control them; the braking resistors (15) being arranged on the casing (12) and the activation switches (16) and the connection switches (17) being grouped in an electrical box (18) fixed to the casing (12).

2. A safety braking device (10) according to claim 1, wherein the braking resistors (15) of each dissipative circuit (14) are arranged in parallel with each other.

3. A safety braking device (10) according to any preceding claim, wherein each of the dissipative circuits (14) is provided with three braking resistors (15).

4. Safety braking device (10) according to claim 3, wherein each of the dissipative circuits (14) is provided with three activation switches (16) of the braking resistors (15).

5. Safety braking device (10) according to any one of the preceding claims, wherein the activation switches (16) and the connection switches (17) are carried by at least one electronic card arranged in the electrical box (18).

6. A safety braking device (10) according to any preceding claim, wherein at least one inductor is arranged in the dissipative circuit (14).

7. Safety braking device (10) according to any one of the claims- preceding indications, wherein at least one of the braking resistors (15) comprises a section extending parallel to the axis of rotation of the rotor (13).

8. Safety braking device (10) according to claims 1 to 7, wherein at least one of the braking resistors (15) comprises a section extending in an arc around the axis of rotation of the rotor (13).

9. An electric motorized system (1), comprising a drive motor and a safety braking device (10) according to any one of the preceding claims, the safety braking device (10) itself being connected to an inverter (80) via a plurality of switches (90), the inverter (80) being connected to an accumulation device.

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